Fluorescent screen and a method of manufacturing the same



Feb. 7, 1939. J. HARTMANN 2,146,573

FLUORESCENT SCREEN AND A METHOD OF MANUFACTURING THE SAME Filed April 24, 1937 -2 Sheets-Sheet l INVENTOR JOSEPH HARTMANN 4' ATTORNEYS Feb. 7, 1939. J. HARTMANN 2, FLUORESCENT SCREEN AND A METHOD OF MANUFACTURING THE SAME Filed April 24, 1937 2 Sheets-Sheet 2 INVENTOR Jose PH HARTMA NN (411 ATT l EY Patented Feb. 7, 1939 I UNITED STATES PATENT oFricE FLUORESCENT SCREEN AND A METHOD OF MANUFACTURING THE.

Joseph Hartmann, Rudolstadt, Germany Application April 24, 1937, Serial No. 138,714 In Germany May 24, 1930 8 Claims. (Cl. 250-80) This invention relates to X-ray photography the sensitized layer of a photographic film or and refers more particularly to fluorescent plate. screens and a method "of manufacturing the The above and other objects of the present insame. v vention may be realized by providing a fluorescent I I 15 The present application is a continuation-inscreen, the base of which will not reflect light part of my co-pending U. S. Patent application emerging from the fluorescent layer. This may Serial No. 536;954,'flled May 12, 1931, which'mabe accomplished, for example, by using a base ,turedintoPatent'No. 2,088,595, issued August 3, which is not only black, but non-reflectant as 1937. l well, or by using a base which is so colored that '10 In the'art-of producing X-ray imagesfluoresit absorbs light rays of those wave lengths which "1 0 ,cent screens are used for the purpose of diminishproduce an image upon the sensitized layer of a ii'ngthe time of exposure during photography. photographic film or plate. I i'l'zheseiscreens comprise a fluorescent layer which For example, the base of a fluorescent screen ;may "or may not -be supported by a base. The may consist of a sheet of cardboard the supportil6 :gfluorescent'layer comprises crystals constituting ing surface of which is covered by a black non- :the fluorescent material of the screen; this crysreflecting paint. 'tallinefluorescent material is embedded in a bind- In the case of fluorescent screens which do not ing material, the binding material and the fluohave a base, the same result may. be ach eved by ,rescent material together constituting the fluocoating the reverse surface of the fluorescent 420 -rescent layer. layer with black non-reflecting paint.

Thefiuorescent screens are usually placed be- I have also found that the fineness of outlines tween the'sourceof X-rays and'a sensitized layer of an X-ray photograph obtained when using a :oi a-photogra-phic film or plate. The purpose of fluorescent screen may be further improved if these screens is'to increase the effect made by the fluorescent layer of the fluorescent screenis 125 the X-rays upon the'sensitized layer. The effect made comparatively thin, for example, .04 mm. of various screens may be measured by ccmparto .08 mm. thick. I ing the efliciencyof light and-consequently, the Practical experiments have shown that when a coefiicient(ii-strengthening of each screen. Natfluorescent layer of such thickness .is used, the -'urall y,;an important aim in constructing the outlines of aphotograph obtained upon afllm .30 screensjs to obtain the best possible efficiency of or plate will be as fine as those of a photograph light and the most favorable coefficient of obtained without the use of the fluorescent screen, strengthening. V provided, of course, that in each case thefilm H A drawback of fluorescent screens known in was blackened in the same way. At the same prior art is that theoutlines of a picture protime the fluorescent screen will diminish the time duce'd-upon a--sensitized layer are much less fine necessary for exposure to a considerable extent.

when fluorescent-screensare used, than would be In other words, a thin fluorescent screen of the thecaseif no-screen were used during'the expodescribed type retains itsadvantage of considersu're. ably diminishing the time necessary for exposure otherwords, while a fluorescent screen perand at the same time does not diminish the fine- -'i'orms the function of increasing the effect of ness of outlines of t e photographic image- 40 X-rays reaching a sensitized layer, this screen at Of course, better results are obtained. .by the the same time produces ablurred picture upon use of afluorescent screen which combines these the-sensitized layer. "features, 1. e. by the use of a fluorescentscreen Heret0f0re, fluorescent screens comprised 3, having a fluorescent layer which is .04 to .08 mm. x "base which was strongly reflecting for the purthick and also having a base the supporting sur- 45 pose of obtaining the greatest possible output of face of which (or the reverse surface of the light. I have discovered that the reason why fluorescent layer) is non-reflectant at least with "fluorescent screens tend to blur 'X-ray photoregard to those rays of light which afiect'the :Igraphsand to diminish the'fineness'of outlines sensitized layerof a film or plate to produce av "thereof isi'due' to theuse of suchreflecting bases. photographic image thereon. V FAniobjectofthepresent invention is the pro- Theeflect of such screen is still further in- ..vision'of a fluorescentscreen which will have an creased if its fluorescent layer is made non-rejadequatez'strengthening:coeflicient and which at flectant with respect to light emerging therefrom. the same time will not diminish the fineness of This may be accomplished by coloring the fluo- 555 -;outlines of an X-ray:photographobtained upon =rescent material, the bindingmaterial, or both,-

with a color or colors which will absorb light of the same wave length as that which is emitted by the fluorescent material.

The invention would appear more clearly from the following detailed description when taken in connection with the accompanying drawings showing by way of example preferred embodiments of the inventive idea.

In the drawings:

Figure 1 is a diagram illustrating the diffusion of light caused by a fluorescent screen.

Figure 2 is a perspective view of a fluorescent screen constructed in accordance with the present invention.

Figure 3 shows a fluorescent screen of a somewhat different type.

Figure 1 shows two sheets or plates 9 and I0 which are made. of lead and which are provided with an opening 8 for the passage of X-rays. The reverse surface ll of the plates 9 and I0 carries a fluorescent layer l3. For simplicitys sake, the binding material constituting a part of the fluorescent layer is not shown at all in the drawings while the crystals i2 constituting the fluorescent material of the fluorescent layer [3 are represented as being cubes although actually they have the shape of a more complicated geometrical figure.

A photographic film 4 is placed over the fluorescent layer It and is in contact therewith.

The X-rays emerging from a source not shown in the drawings pass through the opening 8 and produce a dark spot 5 upon the film 4. However, some of the rays of light are reflected by the crystals and are directed against the surfaces ll of the plates 9 and !0. Then the same light rays are again reflected by the surfaces H and pass through the fluorescent layer l3 until they reach the film 4. These reflected rays of light do not reach the spot 5, but form circles 1 around the spot which diminishes the fineness of outlines of the image produced upon the photographic film 4 Figure 1 indicates that the circles I upon the film 4 may be eliminated by the following two methods:

In the first place, the fluorescent layer i 3 should be made as thin as possible, since then the rays of light will not have to traverse large distances within the fluorescent layer itself, with the result that the circles 1 will be situated much nearer to the spot 5 than would be the case if a comparatively thick fluorescent layer were used. In the second place, the circles 1 may be eliminated entirely, or at least to a substantial extent, by making the surfaces H non-reflectant;

then the light rays reflected by the crystals l2 and falling on the surfaces I i will'be absorbed by thesesurfaces and will not reach the film 4 at all.

Figure 2 shows a fluorescent screen constructed in accordance with the principles of the present invention. This screen comprises a base l3 carrying a fluorescent layer M. As already mentioned, the fluorescent layer it consists of crystalline fluorescent material imbedded in a binding substance; for simplicitys sake, these two component parts of the fluorescent layer are not shown separately in the drawings.

In Figure 2 one corner of the fluorescent layer Hi is shown as being bent away from the base IS in order to indicate that the surface [5 of the base it is non-refiectant, for example, covered with black non-reflectant paint.

As already mentioned, the fluorescent layer M should be comparatively thin. I have found that lines are not necessary, the fluorescent layers may have the usual thickness of .12 to .20 mm.

As shown in Figure 3, it is possible to dispense with the use of the base by coating the surface it of the fluorescent layer I! with a paint which would make the surface l6 non-refiectant, so that it would absorb rays of light reflected upon it by the crystals of the fluorescent layer IT.

The fluorescent material or the binding material, or both the fluorescent material and the binding material, of the fluorescent screens shown in Figures 2 and 3 may be made non-reflectant by coloring it or them with a color or colors which will absorb light of the same wave length as that which is emitted by the. fluorescent material.

What is claimed is:

1. As an article of manufacture, a fluorescent screen for X-ray work, having a fluorescent layer and a base for said layer, wherein that surface of said base which is nearest to said layer is blackened to be non-reflectant with respect to the light emerging from said fluorescent layer, for the purpose of diminishing the reflected and diifused' fluorescent light emerging from parts of said layer. 7

2. As an article of manufacture, a fluorescent screen for X-ray work, having a fluorescent layer and a, base for said layer, wherein that surface of said base which is nearest to said layer is blackened to be non-reflectant and said layer is made non-reflectant by the addition of a pigment with respect to light rays emerging from parts of said layer.

3. As an article of manufacture, a fluorescent screen having a fluorescent layer comprising a fluorescent material and. means for binding said material; and a base for said layer, wherein that surface of said base which is nearest to said layer is blackened to be non-reflectant and said binding means are made non-reflectant by the addition of a pigment with respect to light rays emerging from said fluorescent material.

4. As an article of manufacture, a fluorescent screen having a fluorescent layer comprising a fluorescent material and means for binding said material; and a base for said layer, wherein that surface of said base which is nearest to said layer is blackened to be non-reflectant and said layer is made non-reflectant by the addition of a of a thickness which is less than one tenth of a millimeter and a base for said layer, wherein that surface of said base which is nearest to said layer is blackened to be non-refiectant with respect to light rays emerging from parts of said layer.

7. In a fluorescent screen for X-ray work, a

fluorescent layer having a front surface and a back surface, said fluorescent layer comprising a fluorescent material which reflects the fluorescent light toward said back surface, and blackening means adjacent said back surface for absorbing the reflected fluorescent light.

8. In a fluorescent screen for X-ray work, a fluorescent layer having a front surface and a back surface, said fluorescent layer comprising a fluorescent material which reflects the fluorescent light toward said back surface, and a blackening coating covering said back surface, said coating being for practical purposes non-reflectant with respect to the fluorescent light.

JOSEPH HAR'I'MANN. 

